Being a leader in our field comes naturally to us at ATS.
In helping the defense and intelligence communities complete missions, ATS has earned a reputation as a leader for our work in analytic methodology and technological solutions. Our greatest assets—our engineers, developers, and analysts—are the reason why. Thanks to their innumerable and complementary talents, our expertise in analytics, systems, and data makes us a powerful partner in a very uncertain world.
Meet our experienced leadership team:
David Popelier
Chief Executive Officer (Acting)
General Manager, Mission Technology and Solutions Business Unit
David Popelier is Acting CEO of ATS and the General Manager of ATS’s Mission Technology and Solutions Business Unit. He has more than 20 years of experience serving the national security community, beginning at the State Department as a civil servant and then supporting the IC in both Government staff and contractor roles. Prior to joining ATS in 2020, David managed portfolios of mission-critical contracts for the U.S. Government while at SAIC, LMI, and Oracle; co-founded, grew, and sold the consulting firm FourWinds; and led numerous management consulting engagements with executive-level clients on organizational performance metrics, data analytics and visualization, strategy, communications, and research design.
David holds an MBA from George Mason University, a Master’s degree in National Security Studies from Georgetown University, and a Bachelor’s degree in Spanish and History from the University of Wisconsin-Madison. He is a Certified Analytics Professional and PMI Project Management Professional.
Dave Timmons
Chief Financial Officer
Dave Timmons is the Chief Financial Officer for ATS. He joined the company in 2023, bringing nearly 30 years of financial management experience in both industry and the private sector. Dave most recently served as acting Chief Financial Officer for Empower AI (formerly NCI Information Systems, Inc.). His expertise includes leading mergers and acquisitions and integration of new companies, contributing to company growth through business development, and financial management process improvement. He also brings extensive experience in implementing new accounting standards (including ASC 606 and 842) and liaising with DCAA, DCMA, and external auditors.
Dave holds a degree in Business Administration and Accounting from James Madison University.
April Sullivan
Senior Vice President, Business Development
April Sullivan is the Senior Vice President of Business Development at ATS, bringing over 16 years of experience in business development within the IC and DoD sectors. She has a proven track record of leading high-performing BD and proposal teams, excelling in both large-scale pursuits and organic growth initiatives. She served as the Vice President of Enterprise Proposal Operations at ManTech, where she led a major organizational restructuring within the corporate growth division. Her unique blend of expertise in both business development and proposal operations provide her with unparalleled insight into the interplay between these two critical functions. Her leadership has also shaped growth organizations at Strategic Intelligence Group and SpecTal.
April is a 10-year Air Force Veteran and holds a degree in Multimedia Communications from the Community College of the Air Force.
Shawn Clark
Senior Vice President
General Manager, Cyber, Language & Operations Business Unit
Shawn Clark is the Senior Vice President and General Manager of ATS’s Cyber, Language, and Operations Business Unit. Shawn is ATS’s longest-tenured employee, holding numerous positions and management roles over more than 20 years following his service in the U.S. Army. Shawn’s extensive experience includes supporting IC customers as a Linguist, Targeter, and Program Manager, and prior to his role as BUGM he led ATS’s Mission Technology Division. In addition to his formal leadership roles, Shawn established ATS’s Pillars Program to drive Diversity and Inclusion, promote Philanthropy, support Employee Wellness, and help employee’s take full advantage of their Employee Ownership.
Shawn has a B.S. in Environmental Studies from the American Military University and is a certified PMI Project Management Professional.
Mary Khattak
Vice President, Human Resources
Mary Khattak is ATS’s Vice President of Human Resources, leading total rewards, compliance, HRIS, and employee engagement strategy. Mary is also responsible for corporate giving and community outreach through ATS’s Philanthropy Pillar and strengthening the employee ownership experience through the ESOP Pillar (part of our program of corporate initiatives to best support and engage our employees). Mary is an accomplished human resources executive with more than 25 years of experience with Government contractors and non-profit and for-profit companies. Prior to joining ATS in 2018, Mary was the Human Resources Director at Ace Info Solutions (now part of Guidehouse) and held senior HR positions at SHAPE America, Wolf Trap Foundation, and Wegmans.
Mary holds an MPA from George Mason University and a B.S. in Management from SUNY Geneseo, along with SPHR and SHRM-SCP certifications. She is a member of the Society for Human Resource Management and serves as the President of Dulles SHRM.
Andrea Pattison
Vice President, Contracts and Pricing
Andrea Pattison serves as the Vice President of Contracts and Pricing at ATS, where she leads the company’s contracts, procurement, and pricing functions. With 27 years of extensive experience in contract management-particularly within the defense and intelligence sectors-Andrea brings a wealth of knowledge and leadership to the organization.
Her career includes significant time spent in overseas contingency contracting environments, with assignments in Bosnia, Iraq, and most recently, the Marshall Islands. This global experience has equipped her with a deep understanding of complex, high-stakes contracting operations in dynamic environments.
Andrea holds the Certified Professional Contracts Manager (CPCM) credential, a mark of her commitment to excellence and professionalism in the field. She earned her postgraduate degree in Business Administration from Buckinghamshire Chilterns University College in the UK and holds a Bachelor of Science in Computer Engineering, specializing in cybercriminal profiling.
David Popelier
Chief Executive Officer (Acting)
General Manager, Mission Technology and Solutions Business Unit
David Popelier is Acting CEO of ATS and the General Manager of ATS’s Mission Technology and Solutions Business Unit. He has more than 20 years of experience serving the national security community, beginning at the State Department as a civil servant and then supporting the IC in both Government staff and contractor roles. Prior to joining ATS in 2020, David managed portfolios of mission-critical contracts for the U.S. Government while at SAIC, LMI, and Oracle; co-founded, grew, and sold the consulting firm FourWinds; and led numerous management consulting engagements with executive-level clients on organizational performance metrics, data analytics and visualization, strategy, communications, and research design.
David holds an MBA from George Mason University, a Master’s degree in National Security Studies from Georgetown University, and a Bachelor’s degree in Spanish and History from the University of Wisconsin-Madison. He is a Certified Analytics Professional and PMI Project Management Professional.
Dave Timmons
Chief Financial Officer
Dave Timmons is the Chief Financial Officer for ATS. He joined the company in 2023, bringing nearly 30 years of financial management experience in both industry and the private sector. Dave most recently served as acting Chief Financial Officer for Empower AI (formerly NCI Information Systems, Inc.). His expertise includes leading mergers and acquisitions and integration of new companies, contributing to company growth through business development, and financial management process improvement. He also brings extensive experience in implementing new accounting standards (including ASC 606 and 842) and liaising with DCAA, DCMA, and external auditors.
Dave holds a degree in Business Administration and Accounting from James Madison University.
April Sullivan
Senior Vice President, Business Development
April Sullivan is the Senior Vice President of Business Development at ATS, bringing over 16 years of experience in business development within the IC and DoD sectors. She has a proven track record of leading high-performing BD and proposal teams, excelling in both large-scale pursuits and organic growth initiatives. She served as the Vice President of Enterprise Proposal Operations at ManTech, where she led a major organizational restructuring within the corporate growth division. Her unique blend of expertise in both business development and proposal operations provide her with unparalleled insight into the interplay between these two critical functions. Her leadership has also shaped growth organizations at Strategic Intelligence Group and SpecTal.
April is a 10-year Air Force Veteran and holds a degree in Multimedia Communications from the Community College of the Air Force.
Shawn Clark
Senior Vice President
General Manager, Cyber, Language & Operations Business Unit
Shawn Clark is the Senior Vice President and General Manager of ATS’s Cyber, Language, and Operations Business Unit. Shawn is ATS’s longest-tenured employee, holding numerous positions and management roles over more than 20 years following his service in the U.S. Army. Shawn’s extensive experience includes supporting IC customers as a Linguist, Targeter, and Program Manager, and prior to his role as BUGM he led ATS’s Mission Technology Division. In addition to his formal leadership roles, Shawn established ATS’s Pillars Program to drive Diversity and Inclusion, promote Philanthropy, support Employee Wellness, and help employee’s take full advantage of their Employee Ownership.
Shawn has a B.S. in Environmental Studies from the American Military University and is a certified PMI Project Management Professional.
Mary Khattak
Vice President, Human Resources
Mary Khattak is ATS’s Vice President of Human Resources, leading total rewards, compliance, HRIS, and employee engagement strategy. Mary is also responsible for corporate giving and community outreach through ATS’s Philanthropy Pillar and strengthening the employee ownership experience through the ESOP Pillar (part of our program of corporate initiatives to best support and engage our employees). Mary is an accomplished human resources executive with more than 25 years of experience with Government contractors and non-profit and for-profit companies. Prior to joining ATS in 2018, Mary was the Human Resources Director at Ace Info Solutions (now part of Guidehouse) and held senior HR positions at SHAPE America, Wolf Trap Foundation, and Wegmans.
Mary holds an MPA from George Mason University and a B.S. in Management from SUNY Geneseo, along with SPHR and SHRM-SCP certifications. She is a member of the Society for Human Resource Management and serves as the President of Dulles SHRM.
Andrea Pattison
Vice President, Contracts and Pricing
Andrea Pattison serves as the Vice President of Contracts and Pricing at ATS, where she leads the company’s contracts, procurement, and pricing functions. With 27 years of extensive experience in contract management-particularly within the defense and intelligence sectors-Andrea brings a wealth of knowledge and leadership to the organization.
Her career includes significant time spent in overseas contingency contracting environments, with assignments in Bosnia, Iraq, and most recently, the Marshall Islands. This global experience has equipped her with a deep understanding of complex, high-stakes contracting operations in dynamic environments.
Andrea holds the Certified Professional Contracts Manager (CPCM) credential, a mark of her commitment to excellence and professionalism in the field. She earned her postgraduate degree in Business Administration from Buckinghamshire Chilterns University College in the UK and holds a Bachelor of Science in Computer Engineering, specializing in cybercriminal profiling.